Thioxanthonation of 2-naphthalene-thioacetic acid as a visible-light photoinitiator: The investigation of photophysical and photochemical properties


Keskin Dogruyol S., Dogruyol Z., Özçelik Kazancıoğlu E., Gokcek H., Arsu N.

European Polymer Journal, vol.198, 2023 (SCI-Expanded) identifier

  • Publication Type: Article / Article
  • Volume: 198
  • Publication Date: 2023
  • Doi Number: 10.1016/j.eurpolymj.2023.112440
  • Journal Name: European Polymer Journal
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Academic Search Premier, PASCAL, Aerospace Database, Chemical Abstracts Core, Chimica, Communication Abstracts, Compendex, INSPEC, Metadex, Civil Engineering Abstracts
  • Keywords: Annelated thioxanthone, Fluorescence quantum yield, Laser flash photolysis, Photoinitiator, Photopolymerization, Type II system
  • Yıldız Technical University Affiliated: Yes

Abstract

Thioxanthonation of naphthalene thioacetic acid (TXNPSCH2COOH) resulted a visible light photoinitiator with the high molar absorptivity (ε405: 5680 L.mol−1.cm−1) in the visible spectral region and made this compound an attractive photoinitiator for free radical polymerization reactions. Low fluorescence quantum yield (ΦF: 0.06 in 2-MeTHF) and comparatively low triplet energy (186 kJ/mol in 2-MeTHF) was in favorable for efficient intersystem crossing to the triplet state which is necessary for production of initiating radicals. Indeed, photopolymerization of methyl methacrylate along with TXNPSCH2COOH (1 × 10−3 M) and a tertiary amine namely MDEA yielded nearly 25% conversion of monomer to polymer. All spectrophotometric studies including laser flash photolysis which gives triplet lifetime of initiator which is very important information for initiation mechanism of photoinitiators, indeed a long enough triplet lifetime of TXNPSCH2COOH (τT: 1000 ns) allows for efficient reactions with co-initiators to generate radicals.